Developed by Stanley William Hayter during the late 1960s, Color viscosity printing is among the latest developments in intaglio printmaking.  Using variations of this technique, I start by making a multilayered plate, much deeper than a normal etching. The plate is made of metal (I use  zinc), as in the intaglio processes, and normally  requires very long acid baths. To get around this, I began to construct collagraphs.
In collagraphy, a variety of materials are applied to a rigid underlying layer (such as ragboard or masonite). The word is derived from the Greek word koll or kolla, meaning glue and graph, or the act of drawing. I begin by making collages of cardboard, pasted paper and other textures.  I can ink the resulting plate as an intaglio, or with a roller or paintbrush, or some combination of these. The resulting print is termed a collagraph. Substances such as acrylic texture mediums, sandpapers, cloth, string, or cut cardboard can all be used in creating the plate. Collagraphy is a very open printmaking method. Ink can be applied to the upper surfaces of the plate with a brayer for a relief print, or ink can be applied to the entire board and then removed from the upper surfaces, leaving it in the lower spaces, resulting in an intaglio print.
In my viscosity printing, I combine both intaglio and relief methods. Different tonal effects and vibrant colors result from differences in the depth of relief on an etched plate or collagraph’s highly textured surface. I mix three colors of ink, each of a different viscosity or amount of oiliness, adjusted by adding linseed oil. The plate is inked in several stages. The first ink is fairly dense — of a relatively high viscosity. The high-viscosity ink is applied as in any intaglio process --by forcing it into the recesses of the plate, and then wiping off the plate's surface. Then, I apply ink of a second color, and the thinnest viscosity, to the plate with a hard rubber roller, so that ink only transfers onto the highest areas of the plate. Finally, I apply ink of a third color, and a stiffer consistency, to the middle areas of the plate by using a soft roller. The oily ink on the top layer repels heavier ink, and the third ink, because it is applied with a softer roller, is forced into the indentations of the middle layer. The varying viscosities of the two rolled-on inks prevent them from mixing. Lastly, I place a damp sheet of 100% cotton, acid-free, heavy etching paper over the plate, cover it with felt blankets, and pass it through a press, printing all of the colors simultaneously.
Because I like to experiment with complex combinations of varying colors and viscosities, the process results in unique prints and small editions.